PDS / April Update

I initially waited to construct the new LED matrix until I had a grip on the power requirements. My old board was 2240 LEDs running from a 5V 70A 350W power supply, although it just good enough (I know this because when I run the whole thing at full white, it flickers). However, even as I type this I become unsure of my knowledge — Eric Rosenthal told me that when white LEDs turn yellow that means too much current. Overall, my deficiencies in understanding electricity is something that I wished to address, and measuring power requirements for the new board was a means of doing so.

I started out by scheduled a meeting with Eric Rosenthal, power guru of ITP. He recommended that I first find the “peak instantaneous voltage” of my old LED board by connecting a 1 OHM resistor and using Ohm’s Law to calculate exactly what is the amperage that I require. The different patterns that I displayed drew different amounts of current, depending on how many LEDs were on and what colour the LEDS were.

However I didn’t really do a good job at measuring the current this way. The first 1OHM resistor I used was a tiny one, and when I made the circuit in series, nothing happened. I used other resistors and mostly, nothing happened on the board since there was not enough current. One resistor smoked and I suspect I blew other resistors also.

Later, after consulting with Jeff Feddersen, I learned that different resistors had different Wattage. I would need a much heartier resistor to do what I needed. However, even using 5W and 10W 1OHM resistors in the ITP shop, I still could not calculate what I needed. Time kept ticking and I just wanted to start making the damn thing.

So I decided that if my current power supply worked for a 2240-pixel LED matrix, it would definitely be enough to work on a 1850 and 1900-pixel LED matrix, since I decided to do it in two modules.

PROJECTION SURFACE

I put up the metal L brackets according to plan and the paper was not as tight as I wanted. The thin part of the L bracket could be the culprit. Next steps on this will be to use nails with big heads to increase surface area that sandwiches the paper.

POWER ON THE SIDE

From previous experience I know that each LED strip needs its own connection to the power supply, rather than running the power through the entire strip (which does not do the job). However when I was using a stiff piece of plywood to mount the LED strips to, I could just staple the 12 AWG wire to the board and everything wouldn’t move, including the solder points.

But since I am using a flexible piece of vinyl, I face the challenge of needing a stiff 12 AWG wire soldered to each LED strip, however it needs to be attached to the flexible vinyl. Something stiff attached to something flexible. I consulted Ben Light on this. After the consultation and two hours of deep visualization while sitting on a display rack in Home Depot, I decided upon a low tech solution: I would staple a piece of plywood to the back of the vinyl with heavy-duty staples. And I would staple the 12 AWG to it too. Just like on the old board.